Anionic halogens /pseudohalogens

Addition of halogens and pseudohalogens to the cyclopropylthiocarbene chromium complexes 122 affords the 1,4-dihalo-1-phenylthio-l-alkenes 123 stereoselectively [65]. Electrophilic halogen is likely to activate the carbene complexes, followed by the homo-Michael addition of halide anion. (Scheme 44)... 

There are three important routes to the formation of the mercury-transition metal bond (a) displacement of halogen or pseudohalogen from mercury(II) salts with carbonyl metallate anions (b) reaction of a halo-phenylmercury compound with a transition metal hydride and (c) oxidative addition of a mercury halide to neutral zero valent metals.1 We report here the syntheses of three compounds containing three-centre, two-electron, mercury-ruthenium bonds utilizing trinuclear cluster anions and mercury(II) halides.2-4... 

HCo(CO)4are strong acids in aqueous solution. Both types of anions form precipitates with heavy metal ions such as Ag+ in aqueous solution. The parallels between seven-electron halogen atoms and 17-electron binary carbonyl species are sufficiently strong to justify applying the label pseudohalogen to these carbonyls.29... 

The halogen and pseudohalogen dimer radical anions, X2 (X = Cl, Br, I, SCN), react efficiently with phenols and phenolate ions to give the corresponding phenoxyl radicals (equation 6). 

Another extension is Aat pseudohalogens can replace halogen, so that neutral and anionic isothiocyanates are also accessible by this method [5], as are heterometallic carbonyls [6]. A simple preparation of (Ph3PH)2CoCl4 makes a usefUl undergraduate laboratory experiment [2]. 

Pseudohalogen A linear or planar univalent radical that, like the halogens, can form anions, salts, and covalent derivatives. 

Gulaboski, R., K. Riedl, and R Scholz, Standard Gibbs energies of transfer of halo-genate and pseudohalogenate ions, halogen substituted acetates, and cycloalkyl car-boxylate anions at the water I nitrobenzene interface, Phys Chem Chem Phys, Vol. 5, (2003) p. 1284. 

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